Yeonwoo's brother disappeared years ago, and he's devastated to learn of his death. As he copes with his loss, he's given a pocket watch and learns there's more to his brother's death: he was betrayed while competing in the Tower of the Sun God. Now it's Yeonwoo's turn to use the knowledge his brother left behind. Can Yeonwoo (call sign: Cain) navigate that world and gain enough power and experience to reach the top of the tower, defeating his brother's enemies and all those who stand in his way?